Call-answering device for telephone stations



June 21, 1932. BRAUN 1,864,119

CALL ANSWERING DEVICE FOR TELEPHONE STATIONS Filed March 9, 1951 Fig. 6

M BSWQ [12 vezzzor Patented June 21, 1932 RUDOLE IBBA'UN', F VIENNA, AUSTRIA CALL-ANSWERING DEVICE FOR TELEPHONE STATIONS Application filed March 9, 1981, Serial No. 521,275, and in Austria March 17, 1931.

My invention relates to a device which may be built in or connected to a telephone. station, particularly a subscriber set, and which gives, if in the working position, to an body ringing up this station a clearly audlb e signal. This signal indicates that the call has reached the station and therefore, that line and apparatus are working and may also be used to announce a certain fact, for instance the temporary absence of the subscriber.

My invention is particularly useful on temporary lines or on lines which are frequently interrupted, such as military field-linesand allows an instant testing even in the case that the operator of the called station is absent.

My invention may also be used in cities in connection with a special oflice for the acceptance and deliverance of messages for absent subscribers. In this case, the audible signal not only announces to the caller the fact that the called subscriber is absent but also that a message for the same will be received at and forwarded by the above mentioned oflice.

It is one of the objects of my invention to provide a device of the kind described with a visible indicator showing to the called subscriber as he returns to his set that he has been called during his absence.

The main object of my invention is to provide a simple, inexpensive device for the purpose specified above, which may be used in connection with any existing telephone system, such as local battery (magneto), central battery, machine-switching, and also on twoand four-party lines with selective ringing (A. C. with superimposed D. C.) as well as in connection with private branch extensions and residence-systems without any alteration of the system. The device according to my invention has only very few moving parts, and requires neither spring motors nor batteries or other auxiliary sources of current and does not draw any current from the central battery in the telephone exchange. An-

other object of my invention is to provide a call-answering device which in no case is liable to interfere with the working or operation of the central ofiice equipment.

My invention also aims to provide a callanswering device which gives an audible signal after the ringing current has been shut off, that is with practically all the existing telephone-systems, between the successive ringing periods. The signal produced by the device according to my invention is distinctly difierent from and is not liable to be confounded with any other sound used at present with telephone-systems, such as the busy-sign, the ringing sound or the dial-tone.

My invention also provides a switching device which enables the subscriber to make the device at will operative or inoperative and alternatively to provide for audible signals of several different characters.

The principle on which all the different embodiments of the invention are based is the use of a member capable to oscillate or vibrate freely mechanically which is set in motion by the incoming ringing current by direct action of an electromagnetic device energized by said current. Said member keeps on oscillating for some time (by virtue of its momentum) after the ringing current has been shut off and these free oscillations are used to eflect the signaling. After a number of oscillations the Said member comes to a rest because of the damping by friction, airresistance or the like. The member capable to oscillate may consist of a pendulum, of a weighted spring, of a watch-movement or of any other element capable of slow mechanic oscillations. Alternatively an element may be used which is able to vibrate with an audible freqgency, such as a'tuned fork, bell or gong. roadly spoken, any element having momentum and being influencedby a directional force may be used. Said member may be set in motion by moving it away from'its neutral position by the electro-magnet energized by the ringing current or by a hammer actuated by said electro-magnet which strikes the element capable of mechanic oscillations. The return-signal to the calling subscriber may be produced by making and breaking contacts periodically as the pendulum or the like swings or by varying the magnetic flux in coils connected to the line and arranged in the field of a permanent magnet, as the tuned fork or the like vibrates in front of the poles of said magnet. If contacts are used,

.they ma close and open a local primary cirof the electro-magnet energized by the incoming ringing current without interposing an complicated mechanism. Thus, a simple, e

fective and trouble-proof way i jd d tqw store the power of the incoming nngmg s;

rent and to use this power for the transmission of the return-signal after the end of the ringing period.

Other advantages and features of my inventi on will become clear from the following description with reference to the drawing, in which:

Fig. 1 is the diagram of a device according to the invention for the use with magnetostations with local primary battery.

' Fig. 2 shows also a device for magneto stations which is adapted to give two different signals.

Fig. 3 shows a device for use with centralbattery-stations or in machine switching areas provided with a drop.

Fig. 4 shows a device similar to Fig. 3 adapted to give two different signals.

Fig. 5 is the diagram of a device using a tuned fork and a telephone transmitter.

Fig. 6 is the diagram of a device as shown in Fig. 3 connected'to a four party station through a rectifier.

In the example shown in Fig. 1 of the 1 drawing, 1 is a pendulum provided with an iron bar or armature 2, said armature being arranged in front of the polepieces of an electro-magnet 3. This electro-magnet is provided with two coils 3a and 3b. The coil 3a has a high resistance (say 2000 ohms) and is connected via a switch 4 to terminals 5a and .5?) bridged across the telephone line or connected to the instrument in the same way as the usual auxiliary ringer. The coil 36 is connected in a local circuit including the battery 7, which may be the local primary batpendulum swings back and oscillates for The sound produced is'similar to the ticking of a watch and is very clearly audible in the receiver.

Fig. 2 shows a similar device which is adapted to give two different signals i. e. a ticking sound of the same 'or of twice the frequency of the oscillations of the pendulum. This example shows the use of a condenser 19 of about 2 micro-farad between the line-terminals 15a and 15b and the coil 13a energizing the electro-magnet 13. The

pendulum 11 is in this case a spring or a strip resilient metal bearing on one end the armature 12. The local primary circuit includes the battery'17, the coil 13b and, ac-

cording to the position of the switch'14; one onboth of the contacts 16 and 18 mounted on resilient blades 16a and 18a, respectively.

If only one contact is connected into the circuit, the ticking is slow, if both contacts are used the ticking is more rapid.

Fig. 3 shows a similar device for use on central-battery or machine-switching lines provided with a drop to announce the fact that a call has been received. The pendulum 21 is similar to that of Fig. 2 except that the air-gap between the electro-magnet 23 and the armature 22 is inclined to the axis of the iron-core in order to insure the magnetic action over a greater distance.' The energizing coil 23a is connected over a condenser 29a and a switch 24 to the line-terminals 25a and 25b. 4 The pendulum 21 is connected to one terminal and the contact 26 mounted on the arm 26a to the other terminal over a condenser 296. A drop 32 is provided and normally held in the raised position by a dog 31a ppthe end of a bell-crank lever 31 pivoted at 3 If the electro-magnet 23 is energized by the incoming ringing-current, the pendulum 21 and the armature 22 moves in the position shown in dotted lines. The bell-crank lever 31 is angularly displaced by the armature 22, the dog 31a is raised and releases the drop 32, which falls down in the position shown in dotted lines.

If now the ringing current is shut off and a D. C. voltage is applied to the line, as usual with all C. B. and machine-switching telephone systems the pendulum 21 is released and oscillates. The condenser 29?) is charged every time as the pendulum 21 touches the contact 26 mounted on the resilient blade or arm 26a. This inrush of charging current although by far too weak and too short to actuate the line relay in the telephone exchangeis clearly audible in the receiver of the calling station. To discharge the condenser 29?) while the pendulum 21 swings back, i. e. away from the contact 26, a high resistance in the order of several hundred thousand ohms may be shunted across the signaling condenser 296.

Another way of discharging the signaling condenser which makes it possible to utilize the discharge current for signaling is shown in Fig. 4. This figure also illustrates the use of a watch movement in the place of a pendulum and the use of an individual electromagnet for the drop. This drop is of conventional design and comprises a drop plate 52 held by a bell-crank-lever 51 pivoted at 516 and an electro-magnet 43 with two coils 43a and 4312, the coil 43a being connected in series with the condenser 49a, the coils 53 and the switch 44a across the line terminals 45a and 45?). In front of the pole-pieces of the electro-magnet-coils 53 an armature 42 is mounted on a rotatable shaft 42a and held in the position shown in full lines by a very resilient spiral spring (as used with watch movements) 42?). This spring also serves to connect the armature via a condenser 49?) to- 53. The armature and the contact arm 41,

swings to the position shown in dot and dash lines. If now the ringing current is shut off and D. G. is imposed on the line from the central-office, the armature swings back and forth for some time and touches alternatively the contact springs 46 and 48. If the arm 41 touches the spring 46, the signaling condenser 496 is bridged across the line and charged. If the arm 41 swings back and makes contact with the spring 48, the condenser 496 is discharged either directly over the resistance 50b (to avoid sparking) or through coil 43?) and resistance 50a, according to the position of the switch 446. Thus, it is possible to provide for two different signals consisting of a ticking sound of lower or higher speed, similar as with the device illustrated in Fig. 2.

When using the call-answering device with four-party stations it is necessary that the electro-magnet which actuates the vibrating element is responsibe only to impulses of one predetermined direction. For this purpose, a polarized armature 62 with a biasing spring 61 may be used as shown in Fig. 5. This armature 62 is influenced by an electro-magnet 63 and a polarizing permanent magnet 64. The winding of this electro-magnet is connected to the terminals 65a and 65 which are connected into the circuit of the subscriber set in the same manner as an auxiliary ringer.

Alternatively the electro-magnet 63 may replace the ringer of the station.

A hammer 62 is connected to the armature 62 and strikes, if the electro-magnet 63 is excited with A. C. and super-imposed D. C.

of a certain polarity, the tuned fork or gong 66 which vibrates at an audible frequency. The vibrations of the tuned fork or gong cause a periodical change of the magnetic flux of the permanent magnet 68 through the coils 7 57. The induction current such as generated in the coils 67 is transmitted via a condenser 69 to the terminals 650 and 65d bridged across the line. The effect is that the calling subscriber hears a musical tone in his receiver. $5

This type of call-answering device may be used, of course, also on individual line stations. 1

A way of using the call-answering device as shown in one of the Figures 1-4 on four party lines with selective ringing is illustrated in Fig. 6. In this figure A designates the well-known wiring diagram of a subscriber set (party on tip). The call-answering device B is connected to the ringer R of the set via a rectifier C, preferably of the dry metallic type, which allows only the positive impulses to pass.

My invention is, of course, not limited to the examples shown, any combination of the different features shown in the figures of the drawing being within the scope of the invention. The electro-magnet may be of any suitable form, such as the usual horseshoe type with double coils, or of the barrel-type as commonly used for telephone-relays. The oscillating element may be a suspended or inverted pendulum or of the watch movement type as shown, a swinging column of a liquid enclosed in a U-shaped tube may also be employed. Alternatively a rotatable element may be used, which keeps on turning for some titlfne after the ringing element has been shut o What I claim is le -Inacall-answering device for telephonestations, the combination with an electrorrfagnetic device actuated by the incoming ringing current, of an element adapted to oscillate freely by virtue of its momentum no after being set in motion by said electromagnetic device, and means for converting said free oscillations into electric impulses in a me:

2. Inacall-answering device for telephonestations, the combination with an electromagnet energized by the incoming ringing current, of a pendulum bearing an iron armature arranged in front of the poles of said electro-magnet and adapted to be brought away from its neutral position if said electromagnet is energized, contacts arranged in the swinging path of said pendulum and means for converting the making and breaking of said contacts into electric impulses in a line. 1.

3. In a call-answering device for telephonestations, the combination with an electromagnetic device actuated by the incoming ringing current, of an element adapted to oscillate freely by virtue of its momentum II after bein set in motion by said electromagnetic evice, contacts arranged on both sides in the swinging path of said element, a switch to make operative or inoperative one or both of said contacts, and means for converting the making and breaking of said contacts into electric impulses in the line.

4. In a call-answering device for telephonestations, the combination with an electromagnetic device actuated by the incoming ringing current, of an element adapted to oscillate freely by virtue of its momentum after being set in motion by said electromagnetic device, contacts arranged in the swinging path of said element and a condenser connected to the line by said contacts.

5. Inacall-answering device fortele hone stations, the combination with an e ectromagnetic device actuated by the incoming ringing current, of an. element adapted to oscillate freely by virtue of its momentum after being set in motion by said electromagnetic device, contacts arranged in the swinging path of said element and a condenser shunted b a high resistance connected to the line by said contacts.

6. In a call-answering device fontelephonestations, the combination with an electromagnetic device actuated by the incomin ringing current and including a hammer, o

an element adapted to oscillate freely at an audible frequency by virtue of its momentum after being struck by said hammer, and means for converting the free oscillations of said element into electric impulses in the line.

7. In a call-answering device for telephonestations, the combination with an electromagnetic device actuated by the incoming ringing current and including a hammer, of a tuned fork adapted to oscillate freely at an audible frequency by virtue of its momentum after being struck by said hammer, and a permanent magnet arranged with its poles adjacent to said tuned fork and provided with windings connected to the line.

8. In a call answering device for telephonestations, the combination with an electromagnetic device actuated by the incoming ringing current and connected to the line via a rectifier, of an element adapted to oscillate freely by virtue of its momentum after being set in motion by said electro-magnetic device, and means for converting said free oscillations into electric impulses in the line. In testimony whereof I afiix my signature.

- RUDOLF MAX BRAUN. 

